An American member of al-Qaida issued a stern warning to US President George W. Bush on Tuesday demanding the US leave all Muslim lands or else his country would face an attack worse than September 11, according to a new videotape. Wearing a white robe and a turban, Adam Yehiye Gadahn, who also goes by the name of Azzam al-Amriki, said al-Qaida refuses to negotiate on the demands. "Your failure to heed our demands ... means that you and your people will ... experience things which will make you forget all about the horrors of September 11th, Afghanistan and Iraq and Virginia Tech," he said in the seven-minute video. Gadahn, who is charged in the US with treason for allegedly aiding al-Qaida, spoke in English and the video carried Arabic subtitles. The authenticity of the video could not be verified, but it appeared on a Web site commonly used by Islamic fighters and carried the logo of al-Qaida's media production wing, as-Sahab.